West explosion investigators looking for cause of initial fire

07 May 2013 23:32[Source: ICIS news]

HOUSTON (ICIS)--Investigators have determined through comprehensive interviews with eyewitnesses and an extensive excavation of the blast site that ammonium nitrate was the source of the West Fertilizer explosion. However, authorities said on Tuesday they need more time to conclude the investigation into the cause of the initial fire on 17 April.

State Fire Marshal officials confirmed that while they told the state’s Homeland Security and Public Safety Committee last week that it intended to complete their final report by 10 May, it has become apparent that an additional period of one to two weeks is needed.

At the center of the fact finding is for the multi-agency investigators to determine what caused the fire, in which first responder volunteer firefighters were amongst the 14 casualities. The fire preceded the massive eruption that severely damaged homes, businesses and injured 200 within a 14.9-mile (24km) wide area.

“This is still under investigation. Our main priority is to find the origin and cause of the fire that occurred prior to the explosion,” said Rachel Moreno, spokesperson for the State Fire Marshal’s Office.

“Thus far, investigators do know the origin of the fire was in the fertilizer and seed building," Moreno said. "The investigators continue to work on pinpointing an exact location of the fire’s origin within the building that is over 12,000 square feet [1,115 square metres].”

The building did not contain ammonium nitrate, which according to authorities was located in nearby bins.

West Fertilizer in February had informed state officials that the distributor could be in possession of as much as 270 short tons (244 tonnes) of ammonium nitrate, which is an important crop nutrient for agricultural producers. It also has been used as a key ingredient to create bombs.

It has not been officially determined at this point how much of the chemical was present at the time of the incident, although West Fertilizer officials have said it is believed that the company had about 50 short tons of the substance in storage.

Joining the state agencies in the investigation is the Bureau of Alcohol, Tobacco and Firearms and Explosives (ATF) response team. According to ATF spokesperson Franceska Perot, the federal investigators also need additional time to complete their inquiry.

“It was commonly known that ammonium nitrate was present at the fertilizer facility, but it was verified through the investigation. What is unknown is the amount that was present on that day. That is still under investigation,” said Perot. “We have teams on scene and together with the State Fire Marshal’s Office we have about 65-70 on scene. We will take another one to two weeks.”

The powerful explosion, which occurred 20 minutes after the first call about the fire inside the fertilizer distributor, has left a crater that measures 93 feet wide by 10 feet deep. Investigators said some of the evidence was destroyed by the force of the blast. Other debris was sent as far as 3,000 feet away from the site.

At this point, the examination has resulted in the ruling out of several possible culprits. Officials eliminated natural causes, such as lightning, as well as the company’s four tanks of anhydrous ammonia or a Union Pacific railcar that was initially thought to be containing ammonium nitrate as being factors in igniting the detonation.

Investigators have also determined that the volunteer West firefighters did not cause the blast as they were trying to put out the fire.

“Investigators do know that ammonium nitrate did detonate in the explosion. However, they do not know how the explosion was initiated,” said the Texas Department of Insurance in a statement.

“Additionally water used during the firefighting activities did not contribute to the cause of the explosion," the statement said. "However, the investigation into the deaths of the first responders also continues and is not complete.”

The US Chemical Safety Board (CSB) is also investigating the West incident but from a different viewpoint, according to CSB Managing Director Daniel Horowitz. He said the agency will likely need more time than the accident investigators.

Horowitz said eventually the CSB will issue a report that addresses safety recommendations as well as regulatory issues such as plant site locations and how distributors should be handling and storing hazardous chemicals.

“We are doing a different kind of enterprise that is looking at root causes and how standards and practices should be changed,” said Horowitz. “Our report ultimately becomes public and is intended to be open and transparent.”